I think 2000rpm seems like a sweet spot for cruising. In my V, in 6th at 70mph I am at around 2000rpm even at 55 I can still accelerate in 6th. In traffic on the LIE I go from 1st to 3rd and sometimes stay in gear from 15 mph to 45 mph, less shiftingand braking.
There's so much torque any gear is good, just depends on how much gas I want to use or save. Even driving conservatively around town I have yet to break an average of15mpg. At 70 mph in 6th the instant mpgs read anywhere from 16 to 22 with trying to maintain speed.